This invention relates to silver halide photographic light sensitive materials which contain developing agent precursors.
It is known to use silver halide developing agents for processing silver halide emulsions.
It is also known to incorporate silver halide developing agents into layers of photographic elements having layers of light sensitive silver salts.
Usually, such emulsions, after exposure, are developed by processing them with developing activators such as alkaline solution. This alkaline solution may contain developing agents.
After development by either one of these methods, silver images developed are fixed or stabilized with usual fixing baths such as sodium thiosulfate or thiocyanate baths.
Thus developed and fixed silver halide emulsion layer is then washed with water and dried.
It is convenient to add the developing agent to at least one layer of photographic elements. However, sometimes this is unfavorable because the content of the developing agent decreases during storage due to diffusion, sublimation, etc. Furthermore, developing agents are oxidized even over a relatively short storage to decrease their effects and besides produce colored oxidation products, which cause undesired stains.
One of the methods proposed for overcoming these defects is to add the so-called developing agent precursors to one of the layers of photographic elements.
These developing agent precursors are compounds which do not have developing action before development is carried out and which liberate silver halide developing agents only when they are allowed to contact with appropriate activators.
For example, U.S. Pat. No. 3,295,978 discloses inorganic salts of developing agents (such as lead, calcium, cadmium, barium, etc.), U.S. Pat. No. 3,246,988 discloses halogenated acyl derivatives of hydroquinone, U.S. Pat. No. 3,462,266 discloses oxazine or bisoxazine derivatives of hydroquinone, Japanese Patent Publication (Kokoku) No. 28330/72 discloses aliphatic acyl derivatives of hydroquinone which have quaternary ammonium substituents, and Japanese Patent Publistion (Kokoku) No. 33379/72 discloses lactone type precursors. However, these conventional developing agent precursors are not necessarily satisfactory, namely, some of them do not produce desired developing agents within appropriate periods, have adverse effects on development, are poor in solubility and so substantially are difficult to add to layers of photographic elements, are very difficult to prepare and low in utility, gradually decompose during storage to produce developing agents which become oxidation products upon oxidation to cause undesired stains.
Therefore, those developing agent precursors which cause little staining and keep or provide good photographic speed and desired sensitometries such as density and others have been demanded in this technical field.